feat: initial NixOS home lab infrastructure setup

- Add modular flake-based NixOS configuration
- Implement GitOps foundation with CI/CD pipeline
- Create comprehensive documentation and branching strategy
- Add modular desktop environments (GNOME, Cosmic, Sway)
- Configure virtualization stack (Incus, Libvirt, Podman)
- Set up development tools and hardware-specific modules
- Establish user configuration with literate programming support

This commit represents the completion of Phase 1: Flakes Migration
with modular configuration, virtualization, and GitOps foundation.

overlays/default.nix

@@ -0,0 +1,28 @@
+final: prev: {
+  # Custom packages and overrides for Home-lab infrastructure
+  
+  # Home-lab specific tools and scripts
+  home-lab-tools = final.callPackage ../packages/home-lab-tools.nix { };
+  
+  # Override packages with custom configurations
+  starship = prev.starship.override {
+    # Add any custom starship configuration
+  };
+  
+  # Add unstable packages to stable
+  inherit (final.unstable or {})
+    # Example: latest version of development tools
+    # zed-editor
+    # github-copilot-cli
+  ;
+  
+  # Custom vim/neovim configurations
+  vim-home-lab = prev.vim.override {
+    features = "huge";
+  };
+  
+  # Emacs with custom packages
+  emacs-home-lab = prev.emacs.override {
+    # Custom emacs configuration
+  };
+}